Adult Stuff
by daphrose
Summary: "I don't have a brother, but my college roommate was . . . like a brother to me." - "Was?" - "Yeah, we had a . . . a disagreement a while back. Adult stuff." (Spoilers)


**Hello, Mech-X4 fandom! I have returned! So, if you remember my last story for this show, I theorized that Seth and Leo were actually friends. BINGO! Except, y'know, emphasis on the past tense. And Seth is the Big Bad who was torturing Leo, so . . . hey! I'm still proud of that story, even if it turned out to be mostly wrong. It's "Let's Find Him," if you haven't read it. Anyway!**

 **So this one came out of a line of foreshadowing from Seth (the one in the summary, from the episode "Let's Deal with Our Stuff!"). I was rewatching the series, and Seth said that line, and I literally began to scream. That was** ** _brilliant_** **foreshadowing on the part of the writers. It was such a throw-away line that I didn't even remember it when I heard it the second time, but of course it's referring to Leo. So I took it upon myself to write their "disagreement."**

 **It's worth noting that this takes place years before the series; probably about three or four years before Ryan was born. Also, the building that I mention in this story is NOT the Harper Futuristics headquarters from the show, though it looks similar in many ways. The building I write about is meant to be a much earlier, smaller headquarters for HF, before they moved into the building from the show.**

 **Warnings: Villain talk, end-of-the-world talk, threats, mentions of death and catastrophe. Nothing the show doesn't talk about, so if you're here already, I'm sure it won't bother you. I don't own Mech-X4 or Seth or Leo. Enjoy!**

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 **_— Adult Stuff —_**

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Leo couldn't help but whistle as he walked in a building. His emotions swung between awe and jealousy. The high glass walls, the sleek modern architecture, the new high-tech gadgets at every turn: how could a scientist not fall in love? Leo pushed back his cap and stepped further into the building, approaching the front desk. The lady behind it smiled at him, and he smiled back. Even the receptionist looked at place in this fancy building. She had a sharp tan suit and perfectly straight black hair. Her teeth seemed fake, they were so white. Again, Leo felt that pang of jealousy.

"Can I help you, sir?"

"Yes. I'm Leo Mendel, here to see—"

"Leo!" The voice boomed through the halls, and Leo jumped. He turned to see his best friend strutting down the hall, arms extended. Leo couldn't help but laugh.

"Seth," he said, walking up and clasping his friend's hand. "It's been too long."

"I agree. Time sure flies when you're making millions of dollars, eh?" Seth grinned and turned, gesturing back down the hall. "Come on, let me show you around."

They walked down the most amazing, most pristinely decorated hall Leo had ever seen. Again, he felt that envy, but this time it was accompanied by . . . nausea? Truth be told, everything almost seemed _too_ perfect.

"So," Seth asked, "how's your company been doing?"

"Surprisingly well." Leo chuckled. "We've gotten several contracts in the lsat couple months. And hey, if you ever need someone to test out your products, we're always for hire."

Seth laughed, albeit a bit nervously. "Sorry, I've already got guys that do that."

Leo shrugged. "I figured. It's fine."

" _But_ I can spread your name around. I'm starting to get big sway with some major companies, so I'll be sure to throw in a good word for you."

"Thanks. I'd appreciate that."

They kept going down the hall, and Seth pointed out some of his favorite spots. The customer support room had basketball hoops on every wall. Private meeting rooms had elaborate paintings drawn by some skillful hand. The kitchen had a frozen yogurt bar, complete with only the healthiest of toppings. Every step of the way, Seth had something to be proud of. He didn't outright boast about any of it, but you could see the enthusiasm emanating from his eyes.

Of course Leo felt happy for his friend. Of course he was glad to see Seth go on to do such amazing things. He always knew the guy was capable of it, if he would take his head out the clouds and work on making fantasy a reality. Nonetheless, Leo felt inadequate standing beside his millionaire friend. He owned . . . what? a small testing laboratory with part-time workers? He made more money than most people did, sure, but he felt . . . oddly plain. Seth had created hundreds of jobs and blessed the world with magnificent new tech. Leo had proven that a couple products wouldn't blow up and built miniature fighting robots. Seth would go down in history books, and Leo would be relegated to the background, a minor player in a few minor inventions.

Leo didn't mind the lack of attention. He'd always been uncomfortable in the spotlight, while Seth thrived there. All through college, Leo had seen Seth's quirks embraced and put on display, while his own got mocked and cast out. Again, he didn't mind. He preferred to work in the silence of his own mind, away from the clamoring media outlets and mounting pressure of a massive company. Leo didn't think he could handle a high-tech, high-paced job like that, but that only added to his feeling of inadequacy.

As Seth rambled on, he eventually became aware of Leo's discomfort. He paused and turned to address his friend. "I'm sure you're doing big things too."

Leo shrugged. "Nothing like this. You're a doer, Seth. I'm just a thinker. It's a lot harder for me to get the ideas out of my head and into the world."

"But you will." Seth smiled. "Man, I've seen your journals. You'll change the world too. I know it. Speaking of . . . let's go to my office. There's something I want to show you."

The went up the stairs to face a row of doors on either side and a great double-door at the end. Seth led Leo to that door, his grin growing with every step. They reached it, and Seth threw it open. His office looked like the rest of the building: perfect. In the center was his steel, glass-top desk with a two-monitor setup. To their right sat an ashy-grey polyester couch faced a huge flatscreen TV mounted to the wall. Windows lined three of the walls and displayed a stunning view of the bay. Small gadgets littered every nook and cranny, and despite the rugs covering the wires, Leo stepped on several mere seconds after crossing the threshold.

"Wow," he said, unsure if his mouth could form any other words. He tired to say something else and said, "Wow."

"Isn't it great?"

"Yeah. My office is a closet compared to this. Although, my office is a closet compared to anything," he muttered.

Seth grinned and held up his hands. "And now, for the best part. I'm going to tell you something that will rock your world, my friend. I'm so excited to share this with you. I knew that once I developed the idea, I had to bring you on board."

"What's been going on in that brain of yours?"

"So, _so_ much. Okay, imagine this: a perfect world." Seth held out his hands and pursed his lips. Then he waved over his head and continued, "A world without pollution, or any kind of human contamination, or anything wrong with it!"

"Your dream world."

" _Exactly_. And for years, I though that it was impossible. It's _just_ a dream. Humans are already too far gone. They've already caused too much damage. It can't be undone. Or . . . can it?"

"You're working on a way to fix pollution?"

"Better! I'm working on a way to fix planet Earth."

Leo frowned. "I don't understand."

"Look, Leo, we're too far gone. The only way to fix everything we've done is to start over from scratch. So that's exactly what I'm going to do. I'm going to reset Earth!" Seth held a look of triumph on his face, but it waned when he realized Leo didn't share it. Leo waited a few moments before asking his primary question.

"How?"

Seth sucked in his breath. "That's the big question, isn't it? Well, I don't know _exactly_ how . . . yet! But something . . . catastrophic. Something that will wipe out nearly all human life on Earth and allow us to start a whole new society that respects nature."

Leo allowed those words to sink in. "Wait . . . you want to . . . wipe out humanity?"

"Yeah! Isn't it great? We can destroy everything humans made, and of course we'd immediately solve overpopulation. Sure, it would cause a lot of damage in the short term, but we'll fix it. Then we go back to the way things were millions of years ago, before our taint ruined the world."

"Seth, that plan would kill _billions_ of people."

"Exactly!"

"Seth!"

"Not everyone, of course. I'd select a few that I want to survive with me. And you're one of them! We can rebuild society, but we'll keep it small. We can have a few people running around, but only a few. There will be a lot of strict rules, of course, to make sure we don't repeat our mistakes. It'll be a utopia. So, what do you think? Ready to help me prepare for the end of the world?" Seth addressed his friend with a large smile and his hands outstretched.

Leo shook his head. "If there's a punchline to this, can you please get to it? I do still have work I need to finish today."

Seth's smile fell. "This isn't a joke." He walked over to his computer and tapped a few keys. An image of a spotless green field appeared on the TV screen. It seemed so lifelike that Leo could've sworn he smelled the breeze as it blew past. Seth walked over and stared at it. "Beautiful. And completely unobtainable, unless we start over again."

"So . . . what? You're just going to nuke everyone?"

"No, no, no! Not nukes. Nukes would cause too much damage that would last for thousands of years. I need something fast and easy that will destroy everything in one swift blow. Then my society and I can emerge from our bunker and heal nature."

"And what do you plan to use to destroy the world?"

"That's the part I'm stuck on. That's the part that might take me years or more, but I'm willing to wait. See, I thought of bombs, but someone would probably have to be up above to detonate them, and it would take _so_ many. Nothing nuclear; I already told you why. I need something really, really dangerous, but so far I haven't found it. But I'm looking! And the good news is, it doesn't matter how much pollution happens while I'm searching, because I'll just wipe it out anyway. Win win!" Seth threw his hands in the air and spun around to look out at the bay.

Leo couldn't comprehend this. Seth had always been an environmentalist, a man who sought to put the earth first. Leo had long admired that in him, because he never pushed it too far. Sure, there was that one time that he had genetically modified a plant to eat a guy . . . but no real harm was done! Leo had always seen that as a prank with a purpose, not the malicious act of a madman. But now here he stood, years later, watching his best friend turn giddy at the thought of wiping out billions of lives. He took a deep breath. Surely Seth was just caught up in his idealism. Some common sense would bring him back. Leo walked up and put a gentle hand on Seth's shoulder.

"You know you can't do this, Seth," he said. "I know you. You're not a monster."

"No, I'm not. They are." He swept his hands out, gesturing to . . . the world, Leo supposed. "The monsters are all the ones throughout history who tried to destroy the only planet they have. The monsters are the companies that dump their waste into the oceans. The monsters are the governments with nukes who threaten each other out of fear, the ones who would be willing to destroy the planet just so they can show off their power!"

"That's not what you're doing?"

Seth turned and snarled at Leo. Leo took a step back, afraid for a moment. What had his friend become? He needed a new strategy, fast.

"Think about this, Seth. In order to destroy all the humans, you'd have to destroy all plant and animal life along with it. Ecosystems are fragile things. You'd never be able to rebuild all of them!"

"Yes, I can. With genetic engineering, thousands of DNA samples, and years of research, I can rebuild every ecosystem on the planet. I can bring back all the plants and animals and keep them under control."

"That's not how nature works."

"They'll adapt. It'll be fine."

"With whatever plan you use, you have a high chance of rendering the planet infertile!"

"That's why I've got to pick the best, safest means of destruction. That's why I'm still searching. Leo, I've thought about all of this long and hard. I have a plan! I know it will work!"

"Seth, you cannot do this."

"Why not? Give me one good reason!"

"Gee, I don't know, maybe it's because you'll _kill billions of innocent humans_."

"Ah, ah, ah. We've already established that they're not innocent. They all pollute and ignore the environment. They kill each other and hoard everything they can for themselves. They're the evil ones here, Leo."

"They? So, who are the 'not-they' people you'll bring with you to your new world?"

"Anyone I've chosen who's loyal to me and willing to follow rules."

"Ah-ha! So it's not about creating a perfect new world. It's about setting yourself up as its ruler."

"Why can't it be both? Look, Leo, I'm not a dictator. I'm just the one with the plan who knows exactly how everything needs to be. I'm the one with the vision, so anyone who wants to come with me to the new world will need to accept that. I can't afford them messing it up a second time."

"You know, the only people who have ever talked like that go down in history as tyrants. You think you can build a utopia better than any of them?"

"Yes, because my vision is _perfect_. I just want a better world! What's so wrong with that?"  
Leo stopped for a moment to catch his breath. The two men stood there, staring each other down, waiting and watching for the other one to move. Leo whispered, "If you can't see what's wrong with your plan, then you _are_ a monster, and I'm sorry I didn't see it before."

Seth raised and lowered his arms. He too quieted his voice, sounding eerily calm as he spoke some of the scariest words Leo had ever heard. "I wanted you in my new world, Leo. I still do. Look, this is happening, with or without you. I'll keep searching for a way to start over, and I will succeed. If you don't want to be a part of that, it's your loss, but you'll only wind up dying with the rest of them." He paused for a moment. "I don't want you to die. Leo, join me. Join me and together we'll create paradise."

Leo shook his head. "I'm sorry, Seth. I can't let you do that."

Seth laughed. Not a chuckle, or a even a guffaw. A real, hearty laugh that almost caused Leo to lose his lunch. "What, are you going to try to stop me? How?"

"I'll go to the police."

"And tell them what? That Seth Harper of Harper Futuristics is planning to end the world? They'll never believe you. Check me out. I've got a spotless reputation, and I always put people first. I'm too good and nice to be the bad guy, and everyone knows that."

Leo exhaled. "Wow. You really are an evil genius, aren't you?"

"Evil? Hardly. Genius, absolutely. And I always thought you were one too. I'm sorry you can't see the light, really, I am. But I'm untouchable. My company's worth millions. I've got investors lining up left and right to give me more money. Soon I'll be able to get any piece of technology I want, whenever I want. I'll find something, someway, somehow, and I'll end the world. You can count on that."

"Well." Leo brought his hands up and then slapped them to his thighs. "This is not how I thought today would go. I came in here hoping to see an old friend, but instead, I lost one."  
"I'm sorry we can't see eye-to-eye on this, Leo. Any chance you'll reconsider?"

"Any chance you will?"

"Fine. Then I guess we're done here. Can you see yourself out or do I need to call security?"

"No, no, I can find my way out." Truth be told, Leo didn't quite know his way to the exit, but he didn't want to be walked out by two buff guards. He just wanted to be out and away from the lunatic.

Seth sat down at his desk, his jaw clenched. He began to type while ignoring Leo. Leo stood there for a moment, trying to decide if he should say anything else. He wanted desperately to kick this nasty idea from Seth's head, but he knew it would be futile. After a moment he said, "Goodbye, Harper."

Leo walked out of the room, but right before the doors closed behind him, he heard a quiet, "Goodbye, Mendel."

It took six wrong turns, four helpful directions from employees, and two wall maps for Leo to find his way out of Harper Futuristics. By the time he got outside into the chilly fall air of Bay City, his face ached from holding back the tears. He could hardly comprehend what had happened. He'd lost his best friend and been forewarned about the end of the world in a matter of minutes. What could he do? Seth was right: no one would believe the plan without proof. Most people thought of Seth Harper as a good guy. Eccentric, odd, and uncontrollable at times, but not evil. That was certainly how Leo had viewed him, until today. So, Leo supposed that the task fell to him to stop the end of the world. It was a thought so overwhelming and confounding that Leo actually laughed out loud as he got into his car.

"Well," he whispered to himself, "I guess Seth won't be recommending my services to any of his friends."

Something happened that day. Two best friends broke apart, but that happens every day. People drift away, they fight, and they leave each other behind. But what happened in Seth Harper's office was not a mere falling out, but a declaration of war. Leo would not sit by and let Seth end billions of innocent lives. Seth would not sit by and let Leo find a way to stop him. Two men known for their quirks and humor became cynical that day, loosening their ability to trust.

Someday, someway, somehow, Seth would end the world.

Someday, someway, somehow, Leo would make sure that never happened.

* * *

 **I've gotta say, I really love that this show had an environmentalist for a villain. Those kinds of ideals ("guyzzzz, nature is greater than any human's wellbeing1!112 !") are usually espoused by heroes, so it was good to see it portrayed in an accurate (read: villainous) light. (And here we see the authoress realizing that she's saying something that for some reason is deemed controversial, but choosing not to care one smidgen.)**

 **Also, random fun fact, I had my dad back up my phone to my laptop today, and when he opened my files, the first thing sitting right there is a file titled "Adult Stuff." I don't know if he saw or thought anything about it, but . . . whoops! It's a TV quote, I swear! Also, shout-out to my dad for being the reason I know what a tech company looks like and how they operate. ;)**

 **So, anyway, what'd you think? I know that Seth and Leo weren't quite as humorous as they can be. I figured that a more serious topic warranted the characters displaying their more serious sides. I felt like I actually did a good job considering the situation. And I liked exploration their friendship and the possibility of Leo being just a bit jealous of Seth early on. That kinda sprang out of nowhere when I was writing, but I liked it.**

 **I'm going to be writing a few more Mech-X4 stories soon (hopefully). One with full-blown Ryan whump (which is shockingly missing from a fandom where the** ** _boy gets hurt every time the robot gets hurt_** **), and one or two with Ryan's parents. So follow me if either of those interest you! Reviews are immensely appreciated, but they are not required. I was also a silent reader once. Thank you very much for reading! See you soon!  
**

 **~ Rosie**


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